Multilayer ceramic substrates are used as circuit substrates, equipped with electronic components such as semiconductor chip components, for wiring the electronic components to each other.
As an example of such a multilayer ceramic substrate, Patent Document 1 describes a composite multilayer body including first sheet layers containing a cluster of first powders and second sheet layers containing a cluster of second powders not sintered at a temperature at which at least one portion of the first powder cluster can be melted. In the composite multilayer body described in Patent Document 1, the second sheet layers are interposed between the first sheet layers, both principal surfaces of the composite multilayer body are given by the second sheet layers, the thickness of the second sheet layers laminated in an inner portion of the composite multilayer body is greater than the thickness of the second sheet layers given to the principal surfaces of the composite multilayer body, and portions of the first powder cluster are diffused or fluidized in the second sheet layers and are thereby stuck to each other. Furthermore, Patent Document 1 describes that the first powder cluster contains glass and the second powder cluster contains a ceramic powder such as alumina.
According to Patent Document 1, the composite multilayer body can be manufactured so as to have excellent dimensional accuracy because planar shrinkage during firing can be suppressed by the second powders contained in the second sheet layers.    Patent Document 1: Japanese Patent No. 3554962